In medicine, contrary to common belief, it is not usually enough to know the diagnosis and its best treatment or procedure. Guidelines, checklists, and protocols only go so far when you are treating real people with diverse constitutions for multiple problems under a variety of circumstances.

The more you know about unusual presentations of common diseases, the more likely you are to make the correct diagnosis, I think everyone would agree. Also, the more you know about the rare diseases that can look like the common one you think you see in front of you, rather than having just a memorized list of rule-outs, the better you are at deciding how much extra testing is practical and cost-effective in each situation.

Not everyone with high blood pressure needs to be tested in detail for pheochromocytoma, renal artery stenosis, coarctation of the aorta, Cushing’s syndrome, hyperaldosteronism, hyperparathyroidism, or thyroiditis. But you need to know enough about all of these things to have them in mind, automatically and naturally, when you see someone with high blood pressure.

Just having a lifeless list in your pocket or your EMR, void of vivid details and depth of understanding, puts you at risk of being a burned-out, shallow health care worker someday replaced by apps or artificial intelligence.

The power of knowing these exceptions to the common rules in enough detail to naturally be able to reference them is what makes a doctor a “docere,” a true learned professional.

I recently came across the term “airmanship,” which is when you intimately know your plane, the weather, and the gravitational, centrifugal and all the other physical forces that can alter your flight. Airmanship is taught in rigorous military training that brings you close to the limits of what can be done and far beyond what you will see most days as a commercial pilot, in order to prepare you for those times when everything depends on your judgment.

Primary care medicine may not seem like heroic aerial acrobatics, but it can actually involve a fair amount of flying by the seat of our pants, which must be a real expression straight out of advanced flight school.

Only experience and in-depth knowledge empower you with an appreciation for nuances. Is it necessary to treat mild renal artery stenosis if the blood pressure is easily controlled with medication? A patient with low potassium and high blood pressure probably does have hyperaldosteronism, but do you have to do anything more than prescribe spironolactone regardless of why the potassium runs low?

There is another side to having deep knowledge, besides making you a cost-effective clinician. Patients trust you more if you show that you know a lot about why you’re recommending a certain intervention. And that is not a trivial consideration. Opinions on everything from when life begins and ends to whether coconut oil is good or bad vary so much that what your family doctor says is only one in a crowded field of competing views.

Even guidelines for the most common diseases we treat change too often for patients to feel comfortable just because we tell them that the target numbers or best practices have changed since the last time we saw them.

So, on the most basic level, our demonstrated knowledge in diagnosis and treatment builds case-specific credibility.

Patients usually take great comfort in seeing that you have considered reasonable differential diagnoses and know how the treatment you recommend works and also what to do if the treatment doesn’t work.

But the other consideration is that if we demonstrate a breadth and depth of our medical and scientific knowledge, we also gain broader credibility and authority when we apply our knowledge and understanding of related areas. Obviously, we shouldn’t claim authority in unrelated areas like fashion or finance. That phenomenon, called ultracrepidarianism, has always been rampant in our culture, for instance, in advertisements that more doctors smoke Camels than any other brand of cigarette. But we do have a role as well educated generalists in helping patients evaluate medical news, for example.

The third level is distinctly different from ultracrepidarianism, and that is the authority patients place in our general wisdom, for lack of a more politically correct word; years of schooling and experience with life, disease, and death allow us to say things people need to hear in certain situations. Our words of encouragement, our little gestures of caring, and kindness can have a much greater impact because of the position of authority we may have earned in people’s lives.

I just read a senior psychiatrist’s list of 50 pieces of advice for younger colleagues and his Number 15 really resonated with me: “Try to create rare magic moments—things you say to patients that they will remember always and use in changing their lives.”

This is an earned power that needs to be carefully considered because we can just as easily hurt or undermine our patients if we speak carelessly or impulsively.

Hans Duvefelt, also known as “A Country Doctor,” is a family physician who blogs at A Country Doctor Writes:.

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